• F.F. Bertinelli, N. Catalan-Lasheras, P. Fessia, C. Garion, S.J. Mathot, A. Perin, C.E. Scheuerlein, S. Sgobba, H.H.J. Ten Kate, J.Ph. G. L. Tock, A.P. Verweij, G.P. Willering
  CERN, Geneva

Following the analysis of the September 2008 LHC incident, the assembly process and the quality assurance of the main 13 kA interconnection splices were improved, with new measurement and diagnostics methods introduced. During the 2008-2009 shutdown ~5% of these 10 000 splices were newly assembled with these improvements implemented, but essentially maintaining the original design. It is known today that a limiting factor towards 7 TeV operation is the normal conducting resistance of ~15% of the original main 13 kA interconnection splices, associated to the electrical continuity of the copper stabiliser. A "Splices Task Force" has been set up at CERN to evaluate the need for, develop and test design improvements and prepare the implementation of a consolidation campaign. Important issues of splice design, process choice, resources and time requirements are considered.

• M. Koratzinos, F.F. Bertinelli, Z. Charifoulline, K. Dahlerup-Petersen, R. Denz, C.E. Scheuerlein, R. Schmidt, A.P. Siemko, A.P. Verweij
  CERN, Geneva
• R.H. Flora, H. Pfeffer, J. Strait
  Fermilab, Batavia

At each interconnection between LHC main magnets, a low-resistance solder joint must be made between superconducting cables to provide a continuous current path through the superconductor, and between the surrounding copper stabilizer to provide a current path in case the cable quenches. About 10,000 such joints exist in the LHC. An extensive campaign has been undertaken to characterize and map the resistances of both types of joints. All of the superconducting cable splices were measured using the enhanced protection system of the LHC superconducting circuits. No high-resistance superconductor splices were found above 3 nano-Ohms. Non-invasive measurements of the stabilizer joints were made at 300K in 5 of the 8 sectors, and at 80K in 3 sectors. More precise local measurements were made on suspect interconnects that were opened up, and poor joints were repaired. However, it is likely that additional imperfect stabilizer joints still exist in the LHC. A statistical analysis is used to place bounds on the remaining worst-case resistances. This sets limits on the maximum operating energy of the LHC, prior to a more extensive intervention.